In a dynamic rigid disk storage device, a rotating disk is employed to store information. Rigid disk storage devices typically include a frame to provide attachment points and orientation for other components, and a spindle motor mounted to the frame for rotating the disk. A read/write head is formed on a “head slider” for writing and reading data to and from the disk surface. The head slider is supported and properly oriented in relationship to the disk by a head suspension that provides both the force and compliance necessary for proper head slider operation. As the disk in the storage device rotates beneath the head slider and head suspension, the air above the disk also rotates, thus creating an air bearing which acts with an aerodynamic design of the head slider to create a lift force on the head slider. The lift force is counteracted by a spring force of the head suspension, thus positioning the head slider at a desired height and alignment above the disk which is referred to as the “fly height.”
Head suspensions for rigid disk drives typically include a base plate, load beam and a flexure. The load beam typically includes a mounting region at its proximal end for mounting the head suspension to an actuator of the disk drive, typically at a base plate of the head suspension. The load beam also includes a rigid region and a spring region between the mounting region and the rigid region for providing a spring force to counteract the aerodynamic lift force generated on the head slider during the drive operation as described above. The flexure typically includes a gimbal region having a slider mounting surface where the head slider is mounted. The gimbal region is resiliently moveable with respect to the remainder of the flexure in response to the aerodynamic forces generated by the air bearing. The gimbal region permits the head slider to move in pitch and roll directions to follow disk surface fluctuations.
In one type of head suspension the flexure is formed as a separate piece having a load beam mounting region which is rigidly mounted to the distal end of the load beam using conventional methods such as spot welds. Head suspensions of this type typically include a load point dimple formed in either the load beam or the gimbal region of the flexure. The load point dimple transfers portions of the load generated by the spring region of the load beam, or gram load, to the flexure, provides clearance between the flexure and the load beam, and functions as a point about which the head slider can gimbal in pitch and roll directions to follow fluctuations in the disk surface.
As stated above, head suspensions, as used to support magnetic read/write heads over rotating disks in disk drive units, are typically constructed from multiple components having varying thicknesses. These components may include a load beam, a flexure, a base plate and/or other components. These components are typically welded together to fabricate the head suspension. The thickness of head suspension components typically varies from about 0.001 inches to about 0.010 inches. Ongoing changes in the head suspension industry have created a need for thicker load beams in order to meet the resonance requirements of current head suspensions and disk drives. In addition, multiple piece load beams having thicker rigid sections and thinner spring regions are being used to provide the head suspension characteristics required in current disk drives.
Although these components are relatively small and thin, variations in thickness between components may cause problems in the welding process used to secure the components together. The welding of thicker components may lead to increased weld defects and increased cleaning of the welding system. In addition, set up of the welding process to accommodate differing component thicknesses decreases productivity and may cause other problems in fabrication processes or the head suspension itself.
Prior methods for the welding of head suspension components together included the use of through holes formed in the components at each weld spot so as to leave a small through hole near the center of the weld, as described in U.S. Pat. No. 5,201,458 to Hagen, entitled METHOD OF WELDING A HEAD SUSPENSION ASSEMBLY. Such a through hole would allow for the contraction of the weld upon cooling with a minimum increase in residual stress in the head suspension. Another method included the formation of through holes or partial/blind holes at the weld spots for tubular spot welds, as described in U.S. Pat. No. 4,755,652 to La Rocca, entitled METHOD AND APPARATUS FOR WELDING THIN METAL SHEETS. In this case, the holes have diameters smaller than the desired welds so as to avoid the formation of a core in the weld zone.
There is an ongoing need to improve the welding processes and associated structures available for welding head suspension components together in an efficient and productive manner.